WASHINGTON, Aug. 9 (UPI) — A group of 50 senior foreign policy advisors to Republican presidents dating back to the Richard Nixon administration released a letter Monday slamming current GOP nominee Donald Trump as “dangerous.”

The group, which included Tom Ridge and Michael Chertoff, the first two secretaries of Homeland Security said, Trump, if elected “would be the most reckless president in American history,” and were unanimous is saying they would not vote for him in November.

Perhaps the most searing indictment of Trump’s campaign so far, the letter was printed in the New York Times on Monday.

The letter goes on to slam Trump as lacking “the character, values, and experience to be president,” and as a candidate whose presidency would weaken “U.S. moral authority as the leader of the free world. He appears to lack basic knowledge about and belief in the U.S. Constitution, U.S. laws, and U.S. institutions, including religious tolerance, freedom of the press, and an independent judiciary.”

The group also seems to question Trump’s mental stability saying, “He is unable or unwilling to separate truth from falsehood,” and “He lacks self-control and acts impetuously. He cannot tolerate personal criticism. He has alarmed our closest allies with his erratic behavior. All of these are dangerous qualities in an individual who aspires to be president and commander-in-chief, with command of the U.S. nuclear arsenal.”